Incineration



Jan. 17, 1939. w RAI CH 2,144,507

INCINERATION Filed Dec. 1'7, 1936 INVENTOR WILLIAM RA-ISCH 1J4 ATTORNEY Patented Jan. 17, 1939 UNITED STATES FATE-"T QFFiE INCINERATION' Application December 17, ieseseriamu. 116,385

2 Claims.

The present invention relates to improvements in the treatment of material and especially to treatment in which moisture and volatile matter are removed from the solids, as by a drying operation, and the solids are then burned. This invention, although adapted for the treatment of other materials, is especially adapted for the treatment and disposal ofwaste materials such as garbage and sewage materials including sludge and screenings.

The principal objects of the invention are to provide novel, advantageous and efficient forms of apparatus and methods for effecting treatment of thegeneral character specified.

Another object relates to an improved updraft tiered multiple-hearth furnace-in which part of the-hotcombustion gases is withdrawn from the furnace in the upper part of the burning orlower section of the furnace and the remaining com-. bustion gases arepassed upwardly through the drying or upper section to dry the material passing downwardly'to'the burning section and take up the vapors thus evolved, and then are discharged from the furnace. A further object relates to an improvement in drying and burning material involving the passage of material through a chamber, the supplyof preheated air to one end of the'chamber and the burning of the material at such end, the passage of'air and hot combustion gases toward the other end of the-chamber the withdrawal from theifurnace, at an intermediate point, of a part of the-hotgases, and the withdrawal from the-drying end of the chamber of the hot gases and vapors taken up thereby.

Another object relates to improvements in drying and burning-or'the likerin which material to be treatedis first dried'and then burned while passing through a chamber, a current of air is passed into the outlet portion of the chamber countercurrent to the flow of material to support combustion, and part of the resulting hot combustion gas'passing countercurrent to the material is drawn out of the chamber at an intermediate point and the remainder is drawn through the drying portion and out of the chamber, the'ratio .of the amounts of hot gases passing out at the intermediate part of thechamber and the inlet end of the chamber being varied as desired.

A further object relates to an improvement in which material to be treated is passedthrough a chamber and first dried and then'burned, and a stream of air is introduced atthe other end and together with hot gases resulting from the burning passed countercurrent .to the flow'of material, part of the combustion gases is withdrawn at an intermediate point and part at the drying end, the partremoved; at theintermediate point is used to reheat the part withdrawn from the drying end tovassist in eliminating odors, and the reheated gases are used to preheat the air introduced at the burning part of the chamber.

In carrying out the invention in a preferred form, use maybe made of an updraft tiered multiple-hearth furnace in which material to be treated is introduced at the top and gradually passed downwardly from hearth to hearth through upper drying zones and lower burning zones until-it is discharged from the'bottom of the furnace. Air is introduced'at the bottom of the furnace and hot gases are dischargedirom the upper part in a known manner and in order to control'the furnace part of the hot gases may be removed at an intermediate point whereby the amount of hot gases passing through the drying portion may be controlled and the drying may even be effected at such a low temperature as to avoid the production of noxious odors. The hot gases withdrawn at the intermediate point may be utilized in a heat exchanger to reheat the hot gases laden with moisture vapor which were reduced in temperature whileeffecting the drying, and to eliminate'any odors' evolved in the drying portion The reheated gases may be used to pre= heat air fed to the burning portion. The two streams of discharged gases of combustion-are drawn through the heat exchangers" by induced draft and the proportionate amounts of combuse tion gases'discharged' in the two streams may be varied for purposes of control such as control of the drying operation.

Other objects, features and advantages will appear upon consideration of the following descrip-- tion and of the drawing in which the figure is a sectionalelevation.

Referring to the drawing; there is disclosed a multiple-hearth furnace Ill-comprising a-peripheral wall H, a top l2 and hearths I3, l4, l5, 16,

IT and I8, above-which hearths are corresponding compartments or zones. Preferably the material to be-treated is introduced through the peripheral'part of the top I2, as by means of a hopper l9 and a chute 28 extending through the top l2 and controlled by a pivot-ed door or gate 2| normally urged to closed position by means of a weighted arm-22.

Material introduced into the 'furnace through the hopper l9 and chute 2!! isfed downwardly from hearth to hearth by rabbling it inwardly to central outlets or openings 23 of the hearths. l3, l5 and I1, and outwardly to peripheral. outlets 24 24 at its periphery provided with'a chute 25 con- ,trolled by a pivoted door 26 normally urged to draft furnace, in which there are no gas seals.

closed position by a weighted arm 21.

seal feeding devices such as shown at the top and bottom of the furnace, the doors or gates will open whenever the material accumulates thereon sufficiently to overcome the weighted arms and as soon as the material is discharged from the doors they will close.

The rabbling means may comprisea central hollow driving shaft 28 and one or more arms 29 projecting over each hearth. and provided-with depending blades 30 arranged at such inclinations as to move the material inwardly toward the central outlet 23 in hearths l3, l5 and I1 and toward the peripheral outlets 24 of the hearths I4, I 6 and I8. The shaft 28 passes through the central parts of the central openings 23 of hearths l3, l5 and I! and at the top l2 and hearths l4, l6 and I 8 through smaller openings provided with gas seals. The shaft 28 may be driven by means including a bevel gear 3! on the shaft, a bevel gear 32 meshing with bevel gear 3|, and a pulley 33 driven from any suitable source of power.

In passing downwardly through the furnace, the material is detained temporarily on each hearth and agitated and rabbled toward the outlet or outlets thereof and passes downwardly' therethrough. While passing downwardly through the furnace the material is first dried and then burned which action'is aided by passing a stream of air and hot gases upwardly:

through the furnace that is countercurrent to the flow of the material and'along the path thereof; To this end, air is forced by a fan. 34 through aheat exchanger 35 where it is preheated, and the air thus preheated is passed through a, duct 36 into'a burning compartment or zone in the lower part of the furnace. 1

The air flows upwardly through the burning zones and supports combustion by which hot combustion gases are produced. A part of these gases of combustion flow to the top of the upor valves to divide the furnace into a distinct drying section and a distinct burning section, and pass out of the upper part of the furnace through a duct 37.

In order to control drying of material in the upper partof the furnace and to eliminate noxious odors which may be exolved in the drying, part of the hot combustion gases may be withdrawn from the furnace, at a point intermediate with respect to the upper drying zones and lower burning zones, through a duct 38 and the higher temperature part of a heat exchanger 39 which serves to reheat the gases discharged from the furnace through theduct 31. The gases thus reheated pass to the higher temperature part of the heat exchanger or preheater 35 where they serve to preheat the air supplied to the lower part of the furnace. From the higher tempera.- ture side of the heat exchangers 35 and 39, the combustion gases are drawn through ducts 40 and 4!, respectively, and a duct 42 into which they merge to an induced draft fan' 43 by which they are discharged to a flue or stack 44. The ducts 40 and 4! .may be provided with dampers 45 and 66, respectively, to assist in controlling the operation of the furnace. V

In the event that noxious odors are develmay be eliminated in the heat exchanger 39.

In gas passed through the higher temperature part of heat exchanger 39.

The remaining waste gases' of combustion pass upwardly through the drying zones and take up large volumes ofvapor or steam in connection with a temperature drop to a temperature of from 800' to 900 when these gases are discharged from the upper 'part of the furnace throughthe duct 3'1. From theduct 37, the waste gases pass through the lower temperature side of the heat exchanger 39 and after being reheated therein pass,at a temperature of about 1200", to the higher temperature part of the heat exchanger 35 where inheating the fresh air, the temperature of the combustion gases drops to about 500 as these gases are discharged through duct 48. V I

The gases in the ducts 39 and M are drawn, under control by the dampers 45 and 33, into the duct 12 by the induced draft fan 43; and discharged through the flue or stack 44.

Itshould be understood that various changes may be made and that certain features may be used Without others without departing from the true scope and spirit of the invention.

Having thus described my invention, I claim:

'1. The combination with a multiple hearth furnace in which material is fed downwardly. from hearth. to hearth through compartments above the individual hearths and the material is dried in a pluralityfof drying compartments in the upper part of said furnace and then burned 'in a plurality of burning compartments in the gases of combustion leaving the remainder thereof to pass upwardly through the drying zones and'be reduced in temperature while drying the material, means for withdrawing gases and vapors from the upper compartment of said dry ing compartments and burning odoriferous gases j and vapors in said withdrawn gases and vapors by passing the gases and vapors into heat exchange relationship with the high temperature gases discharged from said upper burning chamber whereby oifensive odors will be eliminated,

' and means for preheating the air introduced into said lower compartment of the burning compartments by heat exchange with the gases and vapors heated by said hot'combustion gases.

' 2. The combination with a multiple hearth furnaoe in which material is fed downwardly from hearth'to hearth through compartments above the individual hearths and the material is dried in a plurality of drying compartments in the upper part ofsaid furnace and then burned in a plurality of; burning compartments in the lower part of the furnace, of a heat exchanger, means for discharging from the upper compartment of said burning compartments part of the high temperature gases of combustion and passing the same through the high temperature side of said heat exchanger, leaving the remainder of the high temperature gases to pass upwardly through the drying zones and be reduced in temperature while drying the material, a second heat exchanger, means for withdrawing gases and vapors from an upper compartment of said drying compartments and passing the same through the low temperature side of the first mentioned heat exchanger to burn odoriferous gases and vapors in the stream from the drying zones and then through the high temperature side of the second heatexchanger and means for passing air through the low temperature side of said second heat exchanger and into a lower compartment of said burning compartments.

WILLIAM RAISCH. 

